Weight-based bandwidth allocation for network traffic

ABSTRACT

A network device may implement packet scheduling with administrator-configurable packet scheduling policies. In one implementation, the network device includes a filter component configured to assign priority levels to data units, the priority levels defining traffic classes for the data units. The network device may also include a scheduler component configured to schedule transmission of the traffic classes based on an assignment of weights to the traffic classes using at least one bandwidth allocation policy that exhibits a bandwidth allocation profile that varies based on one or more parameters of the bandwidth allocation policy that are configurable by an administrator.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/433,364, filed May 15, 2006, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

A. Field of the Invention

Concepts described herein relate generally to network traffic flow, andmore particularly, to weight-based bandwidth allocation for differentclasses of service in a network.

B. Description of Related Art

In an increasingly networked world, more and more traffic, such as data,voice, and video, is transmitted over public and proprietary networks.When routing traffic through the network, it is desirable to be able toassign different types of traffic different priorities as the traffictraverses the network. Some applications require stringent limits onend-to-end traffic delay while other applications require minimalbandwidth guarantees. For example, because streaming video and voicedata, when it is delayed, can result in a noticeable degradation inquality to the end-user, it may be desirable to assign this type oftraffic a higher priority than other traffic.

In Internet Protocol (IP) packet-based networks, each packet may includea header section, a portion of which may be used to indicate the trafficclass to which the packet is assigned. A router at the edge of a networkmay set the traffic class for a packet. Routers in the core of thenetwork may handle the traffic based on the set class. Morespecifically, a router may allocate network resources (such asbandwidth) to traffic classes within the router based on predeterminedbandwidth allocation policies. Typically, within the router, packets ofdifferent traffic queues that are routed to the same output port sharethe link resources of the output port. When the incoming traffic datarate exceeds the output port link capacity, the packets may be bufferedand the bandwidth allocation policies applied.

One known set of techniques for allocating bandwidth are weight-basedscheduling techniques, such as the so-called Weighted Fair Queuing (WFQ)and Weighted Deficit Round Robin (WDRR) techniques. In these techniques,a weight is assigned to each traffic class. The weight assigned to atraffic class determines how often the traffic class should be servedprovided that packets are available to be sent. In other words, theweight associated with a traffic class determines the portion ofbandwidth allocated to the traffic class.

One problem with known weight-based bandwidth allocation techniques isthat they do not define how to assign weights and they may not beflexible enough for different situations. For example, in one situation,an administrator may wish to configure the router to support strictpriority allocation in which higher priority traffic classes are alwaysserved over lower priority classes. In another situation, theadministrator may wish to configure the router to support relativepriority in which different traffic classes may not necessarily beserved with strict priority relative to one another.

There is a need in the art to implement more flexible weight-basedbandwidth allocation techniques.

SUMMARY

In one aspect, a network device includes a filter component configuredto assign priority levels to data units, the priority levels definingtraffic classes for the data units. The network device further includesa scheduler component configured to schedule transmission of the trafficclasses based on an assignment of weights to the traffic classes usingat least one bandwidth allocation policy that exhibits a bandwidthallocation profile that varies based on one or more parameters of thebandwidth allocation policy that are configurable by an administrator.

In another aspect, a method includes assigning priority levels to dataunits, the priority levels defining traffic classes for the data units.The method further includes scheduling transmission of the trafficclasses based on an assignment of weights to the traffic classes usingat least one bandwidth allocation policy that exhibits a bandwidthallocation profile that varies based on one or more parameters that areconfigurable by an administrator. Further, the method includestransmitting the data units in an order corresponding to the assignedweights.

Another aspect is directed to a network device. The network deviceincludes logic to receive data from a first physical link; logic toprocesses the data to determine destination information for the data;and logic to transmit the data on a second physical link in accordancewith the destination information, an order of transmission of the databeing prioritized according to a bandwidth allocation policy. Thebandwidth allocation policy being selected from a first bandwidthallocation policy or a second bandwidth allocation policy. In the firstbandwidth allocation policy, weights associated with priority classes ofthe data are assigned based on first parameters entered by anadministrator and in which two adjacent priority classes have a sameweight difference as any two other adjacent priority classes. In thesecond bandwidth allocation policy, weights associated with the priorityclasses of the data are distributed based on second parameters enteredby an administrator and in which two adjacent priority classes have asame weight ratio as any two other adjacent priority classes.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate an embodiment of the inventionand, together with the description, explain the invention. In thedrawings,

FIG. 1 is an exemplary diagram of a system in which concepts consistentwith the principles of the invention may be implemented;

FIG. 2 is a block diagram illustrating a high-level exemplaryimplementation of one of the edge routers or core routers shown in FIG.1;

FIG. 3 is a diagram illustrating an exemplary composition of a packet;

FIG. 4 is a diagram conceptually illustrating exemplary components forallocating bandwidth in a network device;

FIG. 5 is a flow chart illustrating acts that may be performed inassigning weights based on the equal difference policy;

FIG. 6 is a diagram conceptually illustrating assigning of weights foran exemplary set of parameters based on the acts shown in FIG. 5;

FIG. 7 is a flow chart illustrating acts that may be performed inassigning weights based on the equal ratio policy;

FIG. 8 is a diagram conceptually illustrating assigning of weights foran exemplary set of parameters based on the acts shown in FIG. 7;

FIG. 9 is a diagram illustrating concepts consistent with hybrid weightassignment; and

FIG. 10 is a diagram illustrating an exemplary interface presented by anetwork device for configuring its bandwidth allocation policies.

DETAILED DESCRIPTION

The following detailed description of the invention refers to theaccompanying drawings. The same reference numbers in different drawingsmay identify the same or similar elements. Also, the following detaileddescription does not limit the invention.

As described herein, a network device may implement packet schedulingwith administrator configurable packet scheduling policies. By setting arelatively few number of parameters, the administrator can exercise finecontrol of bandwidth allocation dictated by the packet schedulingpolicies.

Exemplary System Overview

FIG. 1 is an exemplary diagram of a system 100 in which conceptsconsistent with the principles of the invention may be implemented.System 100 may include multiple entities, such as one or more servers120 and one or more clients 125. Servers 120 may include one or morecomputing devices designed to provide information or to otherwiseinteract with clients 125. Similarly, clients 125 may each include oneor more computing devices designed to interact with and obtain contentfrom servers 120 or with other clients 125.

Clients 125 and servers 120 may communicate via a network 140. Network140 may include a wide area network (WAN), such as the Internet, aprivate WAN, or a combination of the Internet and a private WAN, that isused to transport data to servers 120 and clients 125.

Network 140 may include a number of network devices, such as edgerouters 137-1 and 137-2, and core routers 138-1 and 138-2. Edge routers137 may generally function to connect devices, such as clients 125 orservers 120 to network 140. Core routers 138 may function to transmitdata between other routers within network 140. In addition to simplyrouting data, edge routers 137 and core routers 138 may support other“value added” functions, such as quality of service (QoS) features andspecialized security functions, such as IPsec (IP security) encryption.In these situations one or more of core routers 138 and/or edge routers137 may be configured to satisfy a traffic contract in which a minimumQoS is guaranteed for packets within a specified flow or stream.

One of ordinary skill in the art will appreciate that, in practice,system 100 may include other network devices. Additionally, althoughnetwork 140 is primarily described herein as an IP-based network,network 140 could also be an ATM-based network, a frame relay-basednetwork, or a combination of such networks.

FIG. 2 is a block diagram illustrating a high-level exemplaryimplementation of one of edge routers 137 or core routers 138, referredto as router 137/138 herein. Router 137/138 may include packetforwarding engines (PFEs) 201-1 through 201-M (collectively referred toas PFEs 201), an internal switch fabric 205, and a routing engine (RE)210. Router 137/138 may receive data from physical links, process thedata to determine destination information, and transmit the data out ona link in accordance with the destination information.

RE 210 may perform high level management functions for router 137/138.For example, RE 210 may communicate with other networks and systemsconnected to router 137/138 to exchange information regarding networktopology. RE 210 may create routing tables based on the network topologyinformation and forward the routing tables to PFEs 201. PFEs 201 use therouting tables to perform route lookup for incoming data. RE 210 mayalso perform other general control and monitoring functions for router137/138.

PFEs 201 may each connect to each other via switch fabric 205. Switchfabric 205 provides internal links between different PFEs 201. Ingeneral, PFEs 201 receive data on ports connecting physical links thatlead to network 140. Each physical link could be one of many types oftransport media, such as optical fiber or Ethernet cable. The data onthe physical link may be formatted according to one of severalprotocols, such as the synchronous optical network (SONET) standard.PFEs 201 process the received data, determine the correct output portfor the data, and transmit the data on the physical link correspondingto the determined output port.

Exemplary Determination of Priority

Packets traversing a network may be assigned to various priority classes(also called traffic classes herein) and then allocated bandwidthdifferently based on the priority classes. For IP packets, the IP headerportion of the packet is frequently set to indicate the priority levelof the packet.

FIG. 3 is a diagram illustrating an exemplary composition of a packet300. Packet 300 may include a header portion 310, a payload portion 320,and a trailer portion 330. Typically, header portion 310 contains theinformation needed to get the packet from the source to the destination,payload 320 contains the substantive information that is to be carriedby the packet, and trailer portion 330 contains information used toensure that that errors do not occur during transmission of packet 300.

Header portion 310 may contain a number of different fields, including,as is shown in FIG. 3, version field 312, header length field 314, Typeof Service (TOS) field 316, total length field 318, and additionalfields 319. Version field 312 may indicate the format of packet 300,such as an IPv4 packet or an IPv6 packet. Header length field 314 mayindicate the length of the header. TOS field 316 provides an indicationof the priority that is to be assigned to the packet. Total length field318 may indicate the total length of the packet. Additional fields 319represent a number of additional fields that may be included in headerportion 310. These fields will not be described in additional detailherein.

TOS field 316 can be used to determine the priority of the packetrelative to other packets traversing the network. TOS field 316 may bean eight bit field, of which the first three bits, called the precedencebits, may be used to assign a priority value (or level). In someexisting routers, the precedence bits are used to form a priority valuethat the router uses to enforce strict priority. With strict priority,packets of a higher priority level are always given preference overpackets with a lesser priority level.

In other existing routers, the precedence bits may be used withDifferentiated Services techniques to allow more sophisticated bandwidthcontrol using Differentiated Service Code Points (DSCPs). DSCPs containsix bits, of which the first three bits (three precedence bits in TOS)are used to determine a traffic class and the rest are used to determinedrop preference. In Differentiated Services, the first three bits ofDSCP may represent the relative priority level of different trafficclasses. For example, a traffic class with the first three bits of valuefive may not necessarily be served with strict priority over the trafficclass with the first three bits having the value four. Existing DSCPstandards tend to not specify how to determine relative priority.

Bandwidth Allocation

Aspects of the invention provide for flexible allocation of bandwidth ina router or switch. An administrator of the router or switch, by settinga relatively few number of parameters, can exercise fine control ofrelative priority policies of the bandwidth allocation at the router.

FIG. 4 is a diagram conceptually illustrating exemplary components forallocating bandwidth in a network device. In practice, the elementsshown in FIG. 4 may be implemented in, for example, router 137/138, suchas within a PFE 201 of router 137/138.

As shown in FIG. 4, the router may include a filter component 410, ascheduler component 420, and a selector component 430. In general, thesecomponents may act to determine priority for incoming packets andschedule transmission of the packets based on the determined priorityrelative to the priority of other packets. Although bandwidth allocationwill be described as operating on packets, more generally, thetechniques described herein may be applied to frames, cells, or otherdata units in a network device. Additionally, instead of receiving acomplete packet at filter component 410, filter component 410 may onlyreceive header 310 of the packet, a portion of header 310, or some otherdata structure relating to the header of the packet. In this situation,the remainder of the packet may be stored in a different memory and thencombined with an appropriate header before being transmitted.

Filter component 410 may assign a priority level to incoming packetsbased on, for example, TOS field 316 of the packet, or other informationassociated with the packet, such as the output port of the packet. Thepriority level of a packet may define its traffic class. In oneimplementation, filter component 410 may use the first three bits of TOSfield 316 to generate a priority level between the values of zero andseven. Other information associated with the packet may also be used toinfluence the priority level of the packet, such as the source of thepacket or the destination of the packet.

Scheduler component 420 may assign the packets output from filter 410 toan appropriate queue. A queue may store packets (or pointers to packets)of a particular traffic class or of a particular traffic class that isdestined for a particular output port. A number of exemplary queues 450are shown in FIG. 4. Multiple queues may be implemented for a singletraffic class. This is illustrated in FIG. 4 by sets of queues 455-0through 455-N, where each of the N+1 sets may include zero or morequeues. For example, priority class 455-N (i.e., the queues havingpriority level N, the highest priority level) is shown as includingthree distinct queues, labeled as queues 461 through 463. In animplementation in which the first three bits of TOS field 316 are usedto assign priority, N may equal seven, giving eight distinct priorityclasses. Multiple queues may correspond to a single priority class. Insituations in which multiple queues exist for a single traffic class,each of the different queues, such as queues 461, 462, and 463, maycorrespond to a different physical link or a different output port in aPFE 201.

In practice, a single queue may be dedicated to a particular packetflow, stream, or other logical grouping of traffic. Each of queues 450may be implemented as first-in-first-out (FIFO) queues.

Additionally, each queue within a traffic class set 455 may beassociated with a weight. The weights assigned to the queues may used toimplement weighted bandwidth allocation. For example, each weight mayrepresent the portion of the available bandwidth that is to be allocatedto the queue.

Scheduler component 420 may assign the weights to the queues. Schedulercomponent 420 may periodically or intermittently update the weights forqueues 450, such as whenever there is a change in the active queues ortraffic classes. In one implementation, the weights may be assignedbased on weighting policies that are configured by an administrator.Consistent with an aspect of the invention, through the selection of arelatively few parameters, an administrator may configure router 137/138to support one or more relative priority policies.

Selector component 430 may determine which queues to serve (i.e., thequeue from which to dequeue a packet) based on the weights assigned toeach of the queues. For example, the total weight of a link may beapportioned to the queues associated with the link in proportion totheir weights.

A number of different possible weight assignment policies will next bedescribed with reference to FIGS. 5-9. Scheduler component 420 mayassign the queue weights based on these policies.

Equal Difference Series Weight Assignment

Scheduler component 420 may assign weights using a weight assignmentpolicy that will be called an “equal difference series policy” herein.With this policy, two adjacent priority classes will have the sameweight “distance” between one another, which, depending on theapplication, may be a useful technique for providing for relativepriority between traffic classes.

The equal difference series policy will be described in detail withreference to FIGS. 5 and 6.

FIG. 5 is a flow chart illustrating acts that may be performed inassigning weights based on the equal difference series policy. Schedulercomponent 420 may initially receive an indication that the equaldifference series policy is to be used (act 501). An administrator ofrouter 137/138 may, for instance, configure parameters in router 137/138to indicate that this weight assignment policy is desired. Schedulercomponent 420 may also receive parameters for this weight assignmentpolicy (act 502). Specifically, two parameters, called b and d herein,may be used to define the equal difference series policy. The bandwidthallocation profile of the equal difference series policy varies based onthe values of b and d.

Parameter b is called the base and parameter d is called the difference.For each traffic class marked with a specific priority level, denoted aspri(class), a temporal weight, tweight, is calculated (act 503). Thetemporal weight may be defined as:b+pri(class)·d  (Eq. 1).The temporal weights may be summed for all active classes to obtain atotal weight, W (act 504). In other words,W=Σ _(∀active(class)) b+pri(class)·d  (Eq. 2).Each active class may then be assigned a final weight, defined as thetemporal weight of the class divided by the total weight (act 505).Formally, the final weight for a traffic class is:

$\begin{matrix}{\frac{b + {{{pri}({class})} \cdot d}}{W}.} & \left( {{Eq}.\mspace{14mu} 3} \right)\end{matrix}$

FIG. 6 is a diagram conceptually illustrating assigning of weights foran exemplary set of parameters based on the acts shown in FIG. 5. Inthis example, b is set to four and d is set to two. Six queues areshown, each corresponding to a different priority class. Specifically,queue 610 has a priority value of zero, queue 611 has a priority valuethree, queue 612 has a priority value of four, queue 613 has a priorityvalue of five, queue 614 has a priority value of six, and queue 615 hasa priority value of seven. Queue 615 is the highest priority queue whilequeue 610 is the lowest. The temporal weights (Eq. 1) for queues 610through 615 are illustrated in column 620. The total weight, W, is 74.The total weight does not include temporal weight values for priorityvalues one and two because no queues correspond to this weight. Thefinal weights for queues 610 through 615 are shown in column 630. It canbe observed that the difference between any two weights that correspondto adjacent priority classes is a constant (i.e., 2/74 in this example).

A special case of the equal difference series policy can be observedwhen b is set equal to d. In this situation, a traffic class withpriority i gets the weight:

$\begin{matrix}{{{weight}({class})} = {\frac{\left( {{{pri}({class})} + 1} \right)}{\sum\limits_{\forall{{active}{({class})}}}\left( {{{pri}({class})} + 1} \right)}.}} & \left( {{Eq}.\mspace{14mu} 4} \right)\end{matrix}$Intuitively, this situation can be thought of as dividing the linkbandwidth into an aggregate priority number of shares, where eachtraffic class is assigned a weight which is proportional to the priorityof the traffic class.

Equal Ratio Series Weight Assignment

Scheduler component 420 may assign weights using a weight assignmentpolicy that will be called an “equal ratio series policy” herein. Withthis policy, higher priority traffic may be allocated an increasingportion of the bandwidth without starving lower priority traffic.Further, two adjacent priority classes have the same weight ratiobetween one another. This may be useful in the situation such as when itis desired that a traffic class with priority seven take most of thebandwidth while leaving some, but a very little portion, of thebandwidth to traffic classes with a priority lower than seven.

The equal ratio series policy will next be described in detail withreference to FIGS. 7 and 8.

FIG. 7 is a flow chart illustrating acts that may be performed inassigning weights based on the equal ratio series policy. Schedulercomponent 420 may initially receive an indication that the equal ratioseries weight assignment policy is to be used (act 701). Anadministrator of router 137/138 may, for instance, configure parametersin router 137/138 to indicate that this weight assignment policy isdesired. Scheduler component 420 may receive the parameters for thisweight assignment policy (act 702). Specifically, two parameters, calleda and q herein, may be used to define the equal ratio series weightassignment policy. The bandwidth allocation profile of the equal ratioseries policy varies based on the values of a and q.

For each traffic class marked with a specific priority level, denoted aspri(class), a temporal weight, tweight, is calculated (act 703). Thetemporal weight is defined as:a·q^(pri(class))  (Eq. 5).The temporal weights may be summed for all active classes to obtain atotal weight, W (act 704). In other words,W=a·Σ _(∀active(classs)) q ^(pri(class))  (Eq. 6).Each active class may then be assigned a final weight, defined as thetemporal weight of the class divided by the total weight (act 705).Formally, the final weight is:

$\begin{matrix}{\frac{a \cdot q^{{pri}{({class})}}}{W} = {\frac{q^{{pri}{({class})}}}{\sum\limits_{\forall{{active}{({class})}}}q^{{pri}{({class})}}}.}} & \left( {{Eq}.\mspace{14mu} 7} \right)\end{matrix}$

FIG. 8 is a diagram conceptually illustrating assigning of weights foran exemplary set of parameters based on the acts shown in FIG. 7. Inthis example, a is set to nine and q is set to ten. Eight queues areshown, each corresponding to a different priority class. Specifically,queue 810 has a priority value of zero, queue 811 has a priority valueone, queue 812 has a priority value of two, queue 813 has a priorityvalue of three, queue 814 has a priority value of four, queue 815 has apriority value of five, queue 816 has a priority value of six, and queue817 has a priority value of seven. Accordingly, queue 817 is the highestpriority queue while queue 810 is the lowest. The temporal weights forqueues 810 through 817 are illustrated in column 820. The total weightis approximately 11,111,111. The final weights for queues 810 through817 are shown in column 830.

Essentially, the traffic queue with priority seven obtains more than 90%of the bandwidth as long as it has packets to send, while all othertraffic classes share the remaining 10% of the bandwidth. Thiseffectively gives priority to the higher priority traffic classeswithout starving the lower priority classes. Increasing q tends to givehigher priority traffic a more strict preference over lower prioritytraffic. In other words, the higher the value of q, the more strict thepreference of higher priority queues over lower priority queues. At veryhigh values of q, this policy tends to emulate a strict priority policy,in which lower priority queues are not served as long as a higherpriority queue has traffic.

Hybrid Weight Assignment

In some situations, it may be desirable to group traffic classes. Afirst bandwidth allocation policy may be applied at the group level, andwithin each group, a different bandwidth allocation policy may beapplied between the traffic classes in the group. The use of multiplebandwidth allocation policies in this manner will be called “hybridweight assignment” herein.

FIG. 9 is a diagram illustrating concepts consistent with hybrid weightassignment. Eight queues, labeled as queues 910 through 917, are shownin FIG. 9, corresponding to priority classes zero through seven. Queues910 through 913 (priority classes zero through three) are grouped into afirst group 920 and queues 914 through 917 (priority classes fourthrough seven) are grouped into a second group 930. This grouping may beperformed, because, for example, it may be desired that bandwidth beallocated using a combination of both equal difference series weightassignment policies and equal ratio series weight assignment policies.

Referring to the example in FIG. 9, three separate instances of theequal difference series/equal ratio series policies are applied tocreate a hybrid policy. For example, the equal difference series policymay be applied to group I 920 and group II 930. That is, an instance ofthe equal difference series policy may be applied to two “trafficclasses” (groups I and II) to obtain portions of the total bandwidthdedicated to the queues in groups I and II. The group I 920 portion maythen be further allocated among queues 910-913 (four traffic classes)based on another application of the equal difference series or equalratio series policies. Similarly, the group II 930 portion may befurther allocated among queues 914-917 (four traffic classes) based onyet another application of the equal difference series or equal ratioseries policies. In this manner, by using a hybrid weight assignmentpolicy, an administrator can exercise greater control of the weightsassigned to the traffic classes than with either an equal ratio seriespolicy or equal difference series policy applied individually.

The application of the hybrid policy shown in FIG. 9 is one example ofthe hybrid policy. More generally, there are four general situations inwhich the hybrid policy may be applied. Each of these four situationswill now be discussed and will be called case one through case four,respectively.

In case one, the queues within each group may use the equal differenceseries policy while the policy applied among groups is the equal ratioseries policy. All the queues form the different groups are first lumpedtogether and the equal ratio series policy is applied to obtain a firstweight for each queue. A weight is then obtained for each group bysumming the first weights for all of the queues within each group. Foreach individual group, the equal difference series policy is alsoapplied to obtain a second weight for each queue in the group. Theweight obtained for each group may then be multiplied by the secondweight for each queue to obtain the final weight for each queue.

In case two, the queues within each group may use the equal ratio seriespolicy while the policy applied among groups is the equal differenceseries policy. All the queues from the different groups are first lumpedtogether and the equal difference series policy is applied to obtain afirst weight for each queue. A weight is then obtained for each group bysumming the first weights for all of the queues within each group. Foreach individual group, the equal ratio series policy is also applied toobtain a second weight for each queue in the group. The weight obtainedfor each group may then be multiplied by the second weight for eachqueue to obtain the final weight for each queue.

Case three is a special case of case one in which there are two groups.The group with high priority queues uses the equal ratio series policyand the group with lower priority queues uses the equal differenceseries policy. For this policy, use the technique discussed above forcase one to obtain the weight for each queue, but treat each queue inthe high priority group as a separate group (each having one queue). Forexample, assume a high priority group including three queues and a lowerpriority group having four queues. The final weights for each of theseven queues is obtained by applying the techniques for case one inwhich four groups are used by assuming that each of the three queues inthe higher priority group are separate queues.

Case four is a special case of case two in which there are two groups.The group with high priority queues uses the equal difference seriespolicy and the group with lower priority queues uses the equal ratioseries policy. For this policy, use the technique discussed above forcase two to obtain the weight for each queue, but treat each queue inthe high priority group as a separate group (each having one queue). Forexample, assume a high priority group including three queues and a lowerpriority group having four queues. The final weights for each of theseven queues is obtained by applying the techniques for case two inwhich four groups are used by assuming that each of the three queues inthe higher priority group are separate queues.

Exemplary Interface for Setting Bandwidth Allocation Policies

Whether to use the equal difference series, equal ratio series, orhybrid policy may be a configurable by an administrator or other user ofthe network device that implements the policies. The networkadministrator may, for example, manage the network device remotely byconnecting to the network device via a telnet or web session. Theadministrator may then configure the network device to implement thedesired network bandwidth allocation policies.

FIG. 10 is a diagram illustrating an exemplary interface presented by anetwork device for configuring its bandwidth allocation policies. Inthis example, assume that the administrator has logged into the deviceusing a web browser via an HTTP connection. The network device maypresent an interface 1000 through which the administrator can configurethe network device. In the example interface 1000, selection buttons1010 are used to allow the administrator to select the bandwidthallocation policy that the administrator would like to use. Afterselecting a bandwidth allocation policy, the administrator may enter theparameters appropriate for the selected bandwidth allocation policy. Forexample, if the equal difference series policy is selected, theadministrator may then enter the desired values for the b and dparameters in text boxes 1020 and 1025.

CONCLUSION

The foregoing description of exemplary embodiments of the inventionprovides illustration and description, but is not intended to beexhaustive or to limit the invention to the precise form disclosed.Modifications and variations are possible in light of the aboveteachings or may be acquired from practice of the invention.

For example, while a series of acts have been described with regard toFIGS. 5 and 7, the order of the acts may be varied in otherimplementations consistent with the invention. Moreover, non-dependentacts may be implemented in parallel.

It will also be apparent to one of ordinary skill in the art thataspects of the invention, as described above, may be implemented in manydifferent forms of network topologies, software, firmware, and hardwarein the implementations illustrated in the figures. The actual softwarecode or specialized control hardware used to implement aspectsconsistent with the principles of the invention is not limiting of theinvention. Thus, the operation and behavior of the aspects of theinvention were described without reference to the specific softwarecode—it being understood that one of ordinary skill in the art would beable to design software and control hardware to implement the aspectsbased on the description herein.

Further, certain portions of the invention may be implemented as “logic”or as a “component” that performs one or more functions. This logic orcomponent may include hardware, such as an application specificintegrated circuit or a field programmable gate array, software, or acombination of hardware and software.

No element, act, or instruction used in the description of the inventionshould be construed as critical or essential to the invention unlessexplicitly described as such. Also, as used herein, the article “a” isintended to include one or more items. Where only one item is intended,the term “one” or similar language is used. Further, the phrase “basedon” is intended to mean “based, at least in part, on” unless explicitlystated otherwise.

What is claimed:
 1. A method comprising: allocating, by a networkdevice, received data units to a plurality of traffic classes;selecting, via the network device, at least one of a plurality ofbandwidth allocation policies, the plurality of bandwidth allocationpolicies including: a first bandwidth allocation policy that includes apair of weights having respective corresponding weight differences, asecond bandwidth allocation policy that includes a pair of weightshaving respective corresponding weight ratios, and a hybrid bandwidthallocation policy that includes applying the first bandwidth allocationpolicy to two or more pairs of traffic classes, of the plurality oftraffic classes, and applying the second bandwidth allocation policy totwo or more other pairs of traffic classes, of the plurality of trafficclasses; assigning, by the network device, respective weights to theplurality of traffic classes based on the selected at least onebandwidth allocation policy and one or more configurable parameters,assigning the respective weights including: determining a first pair ofweights to be assigned to an adjacent pair of the plurality of trafficclasses, and determining, based on a mathematical relationshipassociated with the first pair of weights, second pairs of weights to beassigned, respectively, to other adjacent pairs of the plurality oftraffic classes; and forwarding the received data units based on theassigned weights.
 2. The method of claim 1, where the hybrid bandwidthallocation policy; applies the first bandwidth allocation policy to twoor more pairs of adjacent traffic classes, of the plurality of trafficclasses, and applies the second bandwidth allocation policy to anothertwo or more pairs of adjacent traffic classes, of the plurality oftraffic classes.
 3. The method of claim 1, further comprising: assigningpriority levels to the received data units based on bits within a Typeof Service (TOS) field obtained from a header of the received dataunits, and where allocating the received data units to the plurality oftraffic classes is further based on the assigned priority levels.
 4. Themethod of claim 1, further comprising: determining a change in a numberof active traffic classes, of the plurality of traffic classes; andupdating the weights for the traffic classes when there is a change in anumber of active traffic classes.
 5. The method of claim 1, where atleast one of: the first bandwidth allocation policy includes twoadjacent traffic classes, or the second bandwidth allocation policyincludes two adjacent traffic classes.
 6. A non-transitory computerreadable medium storing instructions, the instructions comprising: oneor more instructions which, when executed by a processor of a computerdevice, cause the processor to: assign priority levels to data units,the priority levels defining traffic classes for the data units; assignweights to the traffic classes using a plurality of bandwidth allocationpolicies, the plurality of bandwidth allocation policies including:  atleast one of:  a first bandwidth allocation policy that includes twotraffic classes, of the traffic classes, having weight difference thatcorresponds to other weight differences associated with, respectively,two other traffic classes, of the traffic classes, or  a secondbandwidth allocation policy that includes two traffic classes having aweight ratio that corresponds to other weight ratios associated with,respectively, another two other traffic classes, of the traffic classes,and  a hybrid bandwidth allocation policy that includes assigningweights, associated with two or more of the traffic classes, based onthe first bandwidth allocation policy and the second bandwidthallocation policy, and at least one bandwidth allocation policy, of theplurality of bandwidth allocation policies, including a bandwidthallocation profile that varies based on one or more parameters,  theleast one bandwidth allocation policy including assigning the weightssuch that a first mathematical relationship between first weights,associated with two adjacent traffic classes, of the traffic classes,corresponds to a second mathematical relationship between second weightsassociated with another two adjacent traffic classes, of the trafficclasses; and schedule transmission of the traffic classes based on theassigned weights.
 7. The non-transitory computer readable medium ofclaim 6, where at least one of: the two traffic classes included in thefirst bandwidth allocation policy are adjacent traffic classes, or thetwo traffic classes included in the second bandwidth allocation policyare adjacent traffic classes.
 8. The non-transitory computer readablemedium of claim 6, where the one or more instructions to assign theweights to the traffic classes include: one or more instructions toassign the weights to two or more adjacent pairs of traffic classesbased on the first bandwidth allocation policy; and one or moreinstructions to assign the weights to another two or more adjacent pairsof traffic classes based on the second bandwidth allocation policy. 9.The non-transitory computer readable medium of claim 6, where the one ormore parameters, of the at least one bandwidth allocation policy, areconfigurable by a user of the computer device.
 10. The non-transitorycomputer readable medium of claim 6, where the instructions furtherinclude: one or more instructions to transmit the data units inproportion to a weight, of the weights, associated with each of aplurality of queues to store the data units or pointers to the dataunits.
 11. The non-transitory computer readable medium of claim 6, wherethe data units include packets, and the one or more instructions toassign the priority levels to the data units further include: one ormore instructions to assign the priority levels to the packets based onbits within a Type of Service (TOS) field obtained from a header of thepackets.
 12. The non-transitory computer readable medium of claim 6,where the one or more instructions to schedule the transmission of thetraffic classes include: one or more instructions to detect a change inan active traffic class; and one or more instructions to update theweights for the traffic classes based on detecting the change in theactive traffic class.
 13. The non-transitory computer readable medium ofclaim 6, where the hybrid bandwidth allocation policy: applies the firstbandwidth allocation policy to two or more pairs of adjacent trafficclasses, of the traffic classes, and applies the second bandwidthallocation policy to another two or more pairs of adjacent trafficclasses, of the traffic classes.
 14. A device comprising: storage tostore data units; and a processor to: assign the data units to trafficclasses, assign weights to the traffic classes using a plurality ofbandwidth allocation policies, the plurality of bandwidth allocationpolicies including: at least one of:  a first bandwidth allocationpolicy that includes two traffic classes, of the traffic classes, havinga weight difference that corresponds to other weight differencesassociated with, respectively, two other traffic classes, of the trafficclasses, or  a second bandwidth allocation policy that includes twotraffic classes having a weight ratio that corresponds to other weightratios associated with, respectively, another two other traffic classes,of the traffic classes, and a hybrid bandwidth allocation policy thatincludes assigning weights, associated with two or more of the trafficclasses, based on the first bandwidth allocation policy and the secondbandwidth allocation policy, and at least one bandwidth allocationpolicy, of the plurality of bandwidth allocation policies, including abandwidth allocation profile that varies based on one or moreconfigurable parameters, the least one bandwidth allocation policyincluding assigning the weights such that a first mathematicalrelationship between first weights, associated with two adjacent trafficclasses of the traffic classes, corresponds to a second mathematicalrelationship between second weights associated with another two adjacenttraffic classes, of the traffic classes, and schedule transmission ofthe traffic classes based on the assigned weights.
 15. The device ofclaim 14, where at least one of: the two traffic classes included in thefirst bandwidth allocation policy are adjacent traffic classes, or thetwo traffic classes included in the second bandwidth allocation policyare adjacent traffic classes.
 16. The device of claim 14, furthercomprising: a plurality of queues to: store the data units or pointersto the data units, each of the plurality of queues being associated withone of the weights, where the data units are transmitted from the devicein proportion to the weight associated with respective ones of the dataunits stored in each of the plurality of queues.
 17. The device of claim14, where the data units include packets, and the processor, whenassigning the data units to the traffic classes, is further to: assignthe data units to the traffic classes based on bits within a Type ofService (TOS) field obtained from a header of the packets.
 18. Thedevice of claim 14, where the device includes a router.
 19. The deviceof claim 14, where the processor is further to: detect changes in anactive traffic class, of the traffic classes, and update the weights forthe traffic classes based on detecting the change in the active trafficclass.
 20. The device of claim 14, where the hybrid bandwidth allocationpolicy: applies the first bandwidth allocation policy to two or morepairs of adjacent traffic classes, of the traffic classes, and appliesthe second bandwidth allocation policy to another two or more pairs ofadjacent traffic classes, of the traffic classes.